Surgical fluid management systems and methods

ABSTRACT

A surgical fluid management system delivers fluid for distending a uterine cavity to allow cutting and extraction of uterine fibroid tissue, polyps and other abnormal uterine tissue. The system comprises a fluid source, fluid deliver lines, one or more pumps, and a filter for re-circulating the distension fluid between the source and the uterine cavity. A controller can monitor fluid retention by the patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/800,121, filed Jul. 15, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/624,760, filed Sep. 21, 2012, now U.S. Pat. No.9,084,847, which application claims the benefit of U.S. ProvisionalApplication No. 61/538,034, filed Sep. 22, 2011, U.S. ProvisionalApplication No. 61/539,865, filed Sep. 27, 2011, and U.S. ProvisionalApplication No. 61/597,000, filed Feb. 9, 2012, the entire contents ofwhich are incorporated herein by reference in their entirety.

FIELD OF INVENTION

The present invention relates surgical fluid management systems andmethods, for example for use in distending the uterine cavity to allowcutting and extraction of uterine fibroid tissue, polyps and otherabnormal uterine tissue.

BACKGROUND OF INVENTION

Uterine fibroids are non-cancerous tumors that develop in the wall ofuterus. Such fibroids occur in a large percentage of the femalepopulation, with some studies indicating up to 40 percent of all womenhave fibroids. Uterine fibroids can grow over time to be severalcentimeters in diameter and symptoms can include menorrhagia,reproductive dysfunction, pelvic pressure and pain.

One current treatment of fibroids is hysteroscopic resection ormyomectomy which involves transcervical access to the uterus with ahysteroscope together with insertion of a cutting instrument through aworking channel in the hysteroscope. The cutting instrument may be amechanical tissue cutter or an electrosurgical resection device such asa cutting loop. Mechanical cutting devices are disclosed in U.S. Pat.Nos. 7,226,459; 6,032,673 and 5,730,752 and U.S. Published Patent Appl.2009/0270898. An electrosurgical cutting device is disclosed in U.S.Pat. No. 5,906,615.

In a myomectomy or hysteroscopic resection, the initial step of theprocedure includes distention of the uterine cavity to create a workingspace for assisting viewing through the hysteroscope. In a relaxedstate, the uterine cavity collapses with the uterine walls in contactwith one another. A fluid management system is used to distend theuterus to provide a working space wherein a fluid is administeredthrough a passageway in the hysteroscope under sufficient pressure toexpand or distend the uterine cavity. The fluids used to distend theuterus are typically liquid aqueous solutions such as a saline solutionor a sugar-based aqueous solution.

In some RF electrosurgical resection procedures, the distending fluid isa non-conductive aqueous solution to limit RF current conduction.

One particular concern is the fact that fluid management systemstypically administer the fluid under a pressure of up to 100 mm Hg ormore which results in a significant risk that the distending fluid maybe taken up by a cut blood vessel exposed in the uterine cavity. Suchunwanted fluid uptake is known as intravasation, which can lead toserious complications and even death. For this reason, fluid managementsystems have been developed to monitor the patient's fluid uptake on acontinuous basis during a procedure, typically using complicated systemsthat capture, collect and weigh distending fluids that flow through theuterine cavity.

While hysteroscopic resection can be effective in removing uterinefibroids, many commercially available instrument are too large indiameter and thus require anesthesia in an operating room environment.Conventional resectoscopes require cervical dilation to about 9 mm. Whatis needed is a system that can effectively cut and remove fibroid tissuethrough a small diameter hysteroscope.

SUMMARY OF THE INVENTION

The present invention provides improved systems and methods for managingfluid delivery to body spaces, such as a patient's uterus and other bodycavities, during the performance of therapeutic or diagnostic medicalprocedures. The systems will include a fluid source, such as a salineintravenous (IV) fluid bag; fluid lines, such as tubes; conduits;medical flow connectors, such as luers and touhy borst valves; and afilter. Usually, at least one pump will be provided for delivering of afluid from the fluid source to the body space, and recirculate back tothe fluid source after passing through the filter.

Methods according to the present invention will comprise delivering thefluid to the body cavity and performing a therapeutic or a diagnosticprocedure while the fluid distends the body cavity. Body materials, suchas blood and tissue debris, are typically released into the fluid andthe fluid is then recovered from the body cavity and passed through afilter to remove the body materials. The filtered fluid may then bereturned to the fluid source where it is available for recirculation tothe patient.

In a first specific aspect of the present invention, the filtercomprises a hollow fiber filter assembly including a plurality of hollowfibers where the fluid passes through a lumen of each fiber andoutwardly through the porous hollow fiber body to remove at least aportion of the contaminating body materials. Preferably, an additionalfilter element will be provided, usually upstream of the hollow fiberfilter, where the contaminated body fluid will pass first through theadditional filter element which is configured to capture tissue debrisresulting from tissue resection and pass next through the hollow fiberfilter which removes blood and remaining body materials from therecirculating distention fluid.

In specific examples, the hollow fibers will have a total lumen surfacearea of at least about 0.10 m2, usually at least 0.25 m², often at least0.50 m², and frequently at least 1 m². The additional filter willtypically have a pore size which is less than the diameter of the hollowfiber filters. For example, the pore size of the additional filter willtypically be less than 150 microns while the hollow fiber filters willhave a diameter of 200 microns or less. The hollow fibers will also havea nominal molecular weight limit (NMWL) of less than 40 kDa, usuallyless than 30 kDa, and often less than 20 kDa.

In a second aspect of the present invention, the fluid medicalmanagement system will comprise a filter including a plurality of hollowfibers having lumens and at least an additional filter element. A firstfluid line is configured to carry a distention fluid from a fluid sourceto a body space, a second fluid line configured to carry the fluid fromthe body space to the filter, and a third fluid line configured to carryfiltered fluid from the filter back to the fluid source. The filterelement will have a pore size which is less than the diameter of thelumens of the hollow fibers, where the filter element has a pore sizeless than 150 microns and the hollow fibers have a diameter of less than200 microns. In the specific embodiments, the system will furthercomprise a tissue-cutting tool, and the second fluid line will beconfigured to carry fluid and tissue debris such as cut tissue throughthe tissue cutting tool from the body space. The first filter will alsotypically be configured for decoupling from the system to allow thefilter to be removed for transporting cut tissue for pathology or otherpurposes.

In a third aspect of the present invention, the fluid management systemcomprises a first fluid line, a second fluid line, and a third fluidline. A first pump is configured to carry distention fluid from a fluidsource through the first line to a body space. A second pump isconfigured to deliver fluid from the body space through the second lineand through the filter. The filtered fluid is then directed through thethird fluid line from the filter back to the fluid source. The systemfurther comprises a controller and a pressure sensor. The pressuresensor is located in a flow path communicating with the body cavity andprovides intra-cavity pressure signals to the controller. The controlleris configured to control the first and second pumps to maintain aselected pressure in the body cavity in response to the intra-cavitypressure signals. In preferred aspects, the controller operates thefirst pump at a variable rate and the second pump at a fixed rate, wherecontrol of the first pump rate provides the desired pressure control.

In a fourth aspect of the present invention, a medical fluid managementsystem comprises a fluid source having an initial volume, where theinitial volume represents the volume of saline or other distention fluidpresent in the fluid source prior to operation of the system. The systemfurther comprises a filter having a fluid retention volume, where theretention volume is the amount of fluid which will be retained in thefilter during operation of the system. The fluid will not be present inthe filter prior to operation of the system. The system furthercomprises a first fluid line, a second fluid, and a third fluid line.The first fluid line is configured to carry distention fluid from thefluid source to a body space, and the second and third fluid lines areconfigured to recirculate fluid from the body space, through the filterand back to the fluid source. Each of the first fluid line, second fluidline and third fluid line will have retention volumes which representthe amount of recirculating fluid which will be retained in each of thefluid lines during operation of the system. A controller monitors thedifference between (1) the initial volume of the fluid source which ispresent in the system prior to operation and (2) a sum of the volume offluid in the fluid source present at any given time (which will be lessthan that initially present since some of the fluid will be in the fluidlines and filters and some will be resident in the patient) and thecombined fluid retention volumes of the first line, second line, thirdline, and filter. By monitoring the difference, the amount of fluidwhich is resident in the patient at any given time can be followed. Ifthe amount of fluid present in the patient exceeds an expected maximumamount, it can be determined that there is a substantial risk ofintravasion. The system can then react by shutting down, providing analarm, or both.

Typically, the preselected volume of fluid in the patient which is notto be exceeded will be 2.5 liters. The combined fluid retention volumesof first line, second line, third line, and filter will typically beabout 0.5 liters. The material and structure of the hollow fibers may beany of the structures described above, typically including hollow fibershaving a total lumen surface area of at least 0.10 m² and a NMWL of lessthan 40 kDa.

In a fifth aspect of the present invention, the medical fluid managementsystem comprises a filter including both a first tissue-capture filterand a second hollow fiber filter. The first fluid line is configured tocarry distention fluid from a fluid source to a body space. Second andthird fluid lines are configured to recirculate fluid from the bodyspace through the filter assembly and back to the fluid source. At leastone check valve will be positioned intermediate the first and secondfilters to prevent backflow of fluid from the hollow fiber filter to thefirst filter. In specific embodiments, the system will comprise a fourthfluid line joining the first tissue-capture filter and the second hollowfiber filter, where the check valve is present in the fourth line. Infurther specific aspects, the first filter is configured for de-couplingfrom the system to allow removal of cut tissue. The first filter is alsopreferably configured to allow transport of the cut tissue after thefilter has been decoupled from the system. In still further specificaspects, at least one additional check valve may be provided in thesecond fluid line to prevent backflow of fluid from the first filter tothe body and a further additional check valve may be provided in thefirst fluid line for preventing backflow of fluid from the body to thefluid source.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an assembly including a hysteroscope and atissue-cutting device corresponding to the invention that is insertedthrough the working channel of the hysteroscope.

FIG. 2 is a schematic perspective view of a fluid management system usedfor distending the uterus and for assisting in electrosurgical tissuecutting and extraction

FIG. 3 is a cross-sectional view of the shaft of the hysteroscope ofFIG. 1 showing various channels therein.

FIG. 4 is a schematic side view of the working end of theelectrosurgical tissue-cutting device of FIG. 1 showing an outer sleeveand a reciprocating inner sleeve and an electrode arrangement.

FIG. 5 is a schematic perspective view of the working end of the innersleeve of FIG. 4 showing its electrode edge.

FIG. 6A is a schematic cut-away view of a portion of outer sleeve, innerRF cutting sleeve and a tissue-receiving window of the outer sleeve.

FIG. 6B is a schematic view of a distal end portion another embodimentof inner RF cutting sleeve.

FIG. 7A is a cross sectional view of the inner RF cutting sleeve of FIG.6B taken along line 7A-7A of FIG. 6B.

FIG. 7B is another cross sectional view of the inner RF cutting sleeveof FIG. 6B taken along line 7B-7B of FIG. 6B.

FIG. 8 is a schematic view of a distal end portion of another embodimentof inner RF cutting sleeve.

FIG. 9A is a cross sectional view of the RF cutting sleeve of FIG. 8taken along line 9A-9A of FIG. 8.

FIG. 9B is a cross sectional view of the RF cutting sleeve of FIG. 8taken along line 9B-9B of FIG. 8.

FIG. 10A is a perspective view of the working end of the tissue-cuttingdevice of FIG. 1 with the reciprocating RF cutting sleeve in anon-extended position.

FIG. 10B is a perspective view of the tissue-cutting device of FIG. 1with the reciprocating RF cutting sleeve in a partially extendedposition.

FIG. 10C is a perspective view of the tissue-cutting device of FIG. 1with the reciprocating RF cutting sleeve in a fully extended positionacross the tissue-receiving window.

FIG. 11A is a sectional view of the working end of the tissue-cuttingdevice of FIG. 10A with the reciprocating RF cutting sleeve in anon-extended position.

FIG. 11B is a sectional view of the working end of FIG. 10B with thereciprocating RF cutting sleeve in a partially extended position.

FIG. 11C is a sectional view of the working end of FIG. 10C with thereciprocating RF cutting sleeve in a fully extended position

FIG. 12A is an enlarged sectional view of the working end oftissue-cutting device of FIG. 11B with the reciprocating RF cuttingsleeve in a partially extended position showing the RF field in a firstRF mode and plasma cutting of tissue.

FIG. 12B is an enlarged sectional view of the working end of FIG. 11Cwith the reciprocating RF cutting sleeve almost fully extended andshowing the RF fields switching to a second RF mode from a first RF modeshown in FIG. 12.

FIG. 12C is an enlarged sectional view of the working end of FIG. 11Cwith the reciprocating RF cutting sleeve again almost fully extended andshowing the explosive vaporization of a captured liquid volume to expelcut tissue in the proximal direction.

FIG. 13 is an enlarged perspective view of a portion of the working endof FIG. 12C showing an interior chamber and a fluted projecting element.

FIG. 14 is a sectional view of the working end of FIG. 12C showing aninterior chamber and a variation of a projecting element.

FIG. 15 is a sectional view of the working end of FIG. 12C showing aninterior chamber and a variation of a projecting element configured toexplosively vaporize the captured liquid volume.

FIG. 16 is a schematic view of a system for fibroid removal including afluid management system.

FIG. 17 is a schematic view of the fluid management system of FIG. 16with an enlarged view of the working end of a tissue-cutting probe asgenerally described in FIGS. 1-12C in a position to cut and remove afibroid.

FIG. 18 is a cut-away schematic view of a filter module of the fluidmanagement system of FIGS. 16-17.

DETAILED DESCRIPTION

FIG. 1 illustrates an assembly that comprises an endoscope 50 used forhysteroscopy together with a tissue-extraction device 100 extendingthrough a working channel 102 of the endoscope. The endoscope orhysteroscope 50 has a handle 104 coupled to an elongated shaft 105having a diameter of 5 mm to 7 mm. The working channel 102 therein maybe round, D-shaped or any other suitable shape. The endoscope shaft 105is further configured with an optics channel 106 and one or more fluidinflow/outflow channels 108 a, 108 b (FIG. 3) that communicate withvalve-connectors 110 a, 110 b configured for coupling to a fluid inflowsource 120 thereto, or optionally a negative pressure source 125 (FIGS.1-2). The fluid inflow source 120 is a component of a fluid managementsystem 126 as is known in the art (FIG. 2) which comprises a fluidcontainer 128 and pump mechanism 130 which pumps fluid through thehysteroscope 50 into the uterine cavity. As can be seen in FIG. 2, thefluid management system 126 further includes the negative pressuresource 125 (which can comprise an operating room wall suction source)coupled to the tissue-cutting device 100. The handle 104 of theendoscope includes the angled extension portion 132 with optics to whicha videoscopic camera 135 can be operatively coupled. A light source 136also is coupled to light coupling 138 on the handle of the hysteroscope50. The working channel 102 of the hysteroscope is configured forinsertion and manipulation of the tissue-cutting and extracting device100, for example to treat and remove fibroid tissue. In one embodiment,the hysteroscope shaft 105 has an axial length of 21 cm, and cancomprise a 0° scope, or 15° to 30° scope.

Still referring to FIG. 1, the tissue-cutting device 100 has a highlyelongated shaft assembly 140 configured to extend through the workingchannel 102 in the hysteroscope. A handle 142 of the tissue-cuttingdevice 100 is adapted for manipulating the electrosurgical working end145 of the device. In use, the handle 142 can be manipulated bothrotationally and axially, for example, to orient the working end 145 tocut targeted fibroid tissue. The tissue-cutting device 100 hassubsystems coupled to its handle 142 to enable electrosurgical cuttingof targeted tissue. A radio frequency generator or RF source 150 andcontroller 155 are coupled to at least one RF electrode carried by theworking end 145 as will be described in detail below. In one embodimentshown in FIG. 1, an electrical cable 156 and negative pressure source125 are operatively coupled to a connector 158 in handle 142. Theelectrical cable couples the RF source 150 to the electrosurgicalworking end 145. The negative pressure source 125 communicates with atissue-extraction channel 160 in the shaft assembly 140 of the tissueextraction device 100 (FIG. 4).

FIG. 1 further illustrates a seal housing 162 that carries a flexibleseal 164 carried by the hysteroscope handle 104 for sealing the shaft140 of the tissue-cutting device 100 in the working channel 102 toprevent distending fluid from escaping from a uterine cavity.

In one embodiment as shown in FIG. 1, the handle 142 of tissue-cuttingdevice 100 includes a motor drive 165 for reciprocating or otherwisemoving a cutting component of the electrosurgical working end 145 aswill be described below. The handle 142 optionally includes one or moreactuator buttons 166 for actuating the device. In another embodiment, afootswitch can be used to operate the device. In one embodiment, thesystem includes a switch or control mechanism to provide a plurality ofreciprocation speeds, for example 1 Hz, 2 Hz, 3 Hz, 4 Hz and up to 8 Hz.Further, the system can include a mechanism for moving and locking thereciprocating cutting sleeve in a non-extended position and in anextended position. Further, the system can include a mechanism foractuating a single reciprocating stroke.

Referring to FIGS. 1 and 4, an electrosurgical tissue-cutting device hasan elongate shaft assembly 140 extending about longitudinal axis 168comprising an exterior or first outer sleeve 170 with passageway orlumen 172 therein that accommodates a second or inner sleeve 175 thatcan reciprocate (and optionally rotate or oscillate) in lumen 172 to cuttissue as is known in that art of such tubular cutters. In oneembodiment, the tissue-receiving window 176 in the outer sleeve 170 hasan axial length ranging between 10 mm and 30 mm and extends in a radialangle about outer sleeve 170 from about 45° to 210° relative to axis 168of the sleeve. The outer and inner sleeves 170 and 175 can comprise athin-wall stainless steel material and function as opposing polarityelectrodes as will be described in detail below. FIGS. 6A-8 illustrateinsulative layers carried by the outer and inner sleeves 170 and 175 tolimits, control and/or prevent unwanted electrical current flows betweencertain portions go the sleeve. In one embodiment, a stainless steelouter sleeve 170 has an O.D. of 0.143″ with an I.D. of 0.133″ and withan inner insulative layer (described below) the sleeve has a nominalI.D. of 0.125″. In this embodiment, the stainless steel inner sleeve 175has an O.D. of 0.120″ with an I.D. of 0.112″. The inner sleeve 175 withan outer insulative layer has a nominal O.D. of about 0.123″ to 0.124″to reciprocate in lumen 172. In other embodiments, outer and or innersleeves can be fabricated of metal, plastic, ceramic of a combinationthereof. The cross-section of the sleeves can be round, oval or anyother suitable shape.

As can be seen in FIG. 4, the distal end 177 of inner sleeve 175comprises a first polarity electrode with distal cutting electrode edge180 about which plasma can be generated. The electrode edge 180 also canbe described as an active electrode during tissue cutting since theelectrode edge 180 then has a substantially smaller surface area thanthe opposing polarity or return electrode. In one embodiment in FIG. 4,the exposed surfaces of outer sleeve 170 comprises the second polarityelectrode 185, which thus can be described as the return electrode sinceduring use such an electrode surface has a substantially larger surfacearea compared to the functionally exposed surface area of the activeelectrode edge 180.

In one aspect of the invention, the inner sleeve or cutting sleeve 175has an interior tissue extraction lumen 160 with first and secondinterior diameters that are adapted to electrosurgically cut tissuevolumes rapidly—and thereafter consistently extract the cut tissuestrips through the highly elongated lumen 160 without clogging. Nowreferring to FIGS. 5 and 6A, it can be seen that the inner sleeve 175has a first diameter portion 190A that extends from the handle 142(FIG. 1) to a distal region 192 of the sleeve 175 wherein the tissueextraction lumen transitions to a smaller second diameter lumen 190Bwith a reduced diameter indicated at B which is defined by the electrodesleeve element 195 that provides cutting electrode edge 180. The axiallength C of the reduced cross-section lumen 190B can range from about 2mm to 20 mm. In one embodiment, the first diameter A is 0.112″ and thesecond reduced diameter B is 0.100″. As shown in FIG. 5, the innersleeve 175 can be an electrically conductive stainless steel and thereduced diameter electrode portion also can comprise a stainless steelelectrode sleeve element 195 that is welded in place by weld 196 (FIG.6A). In another alternative embodiment, the electrode and reduceddiameter electrode sleeve element 195 comprises a tungsten tube that canbe press fit into the distal end 198 of inner sleeve 175. FIGS. 5 and 6Afurther illustrates the interfacing insulation layers 202 and 204carried by the first and second sleeves 170, 175, respectively. In FIG.6A, the outer sleeve 170 is lined with a thin-wall insulative material200, such as PFA, or another material described below. Similarly, theinner sleeve 175 has an exterior insulative layer 202. These coatingmaterials can be lubricious as well as electrically insulative to reducefriction during reciprocation of the inner sleeve 175.

The insulative layers 200 and 202 described above can comprise alubricious, hydrophobic or hydrophilic polymeric material. For example,the material can comprise a bio-compatible material such as PFA,TEFLON®, polytetrafluroethylene (PTFE), FEP (Fluorinatedethylenepropylene), polyethylene, polyamide, ECTFE(Ethylenechlorotrifluoroethylene), ETFE, PVDF, polyvinyl chloride orsilicone.

Now turning to FIG. 6B, another variation of inner sleeve 175 isillustrated in a schematic view together with a tissue volume beingresected with the plasma electrode edge 180. In this embodiment, as inother embodiments in this disclosure, the RF source operates at selectedoperational parameters to create a plasma around the electrode edge 180of electrode sleeve 195 as is known in the art. Thus, the plasmagenerated at electrode edge 180 can cut and ablate a path P in thetissue 220, and is suited for cutting fibroid tissue and other abnormaluterine tissue. In FIG. 6B, the distal portion of the cutting sleeve 175includes a ceramic collar 222 which is adjacent the distal edge 180 ofthe electrode sleeve 195. The ceramic 222 collar functions to confineplasma formation about the distal electrode edge 180 and functionsfurther to prevent plasma from contacting and damaging the polymerinsulative layer 202 on the cutting sleeve 175 during operation. In oneaspect of the invention, the path P cut in the tissue 220 with theplasma at electrode edge 180 provides a path P having an ablated widthindicated at W, wherein such path width W is substantially wide due totissue vaporization. This removal and vaporization of tissue in path Pis substantially different than the effect of cutting similar tissuewith a sharp blade edge, as in various prior art devices. A sharp bladeedge can divide tissue (without cauterization) but applies mechanicalforce to the tissue and may prevent a large cross section slug of tissuefrom being cut. In contrast, the plasma at the electrode edge 180 canvaporize a path P in tissue without applying any substantial force onthe tissue to thus cut larger cross sections or slugs strips of tissue.Further, the plasma cutting effect reduces the cross section of tissuestrip 225 received in the tissue-extraction lumen 190B. FIG. 6B depictsa tissue strip to 225 entering lumen 190B which has such a smallercross-section than the lumen due to the vaporization of tissue. Further,the cross section of tissue 225 as it enters the larger cross-sectionlumen 190A results in even greater free space 196 around the tissuestrip 225. Thus, the resection of tissue with the plasma electrode edge180, together with the lumen transition from the smaller cross-section(190B) to the larger cross-section (190A) of the tissue-extraction lumen160 can significantly reduce or eliminate the potential for successiveresected tissue strips 225 to clog the lumen. Prior art resectiondevices with such small diameter tissue-extraction lumen typically haveproblems with tissue clogging.

In another aspect of the invention, the negative pressure source 225coupled to the proximal end of tissue-extraction lumen 160 (see FIGS. 1and 4) also assists in aspirating and moving tissue strips 225 in theproximal direction to a collection reservoir (not shown) outside thehandle 142 of the device

FIGS. 7A-7B illustrate the change in lumen diameter of cutting sleeve175 of FIG. 6B. FIG. 8 illustrates the distal end of a variation ofcutting sleeve 175′ which is configured with an electrode cuttingelement 195′ that is partially tubular in contrast to the previouslydescribed tubular electrode element 195 (FIGS. 5 and 6A). FIGS. 9A-9Bagain illustrate the change in cross-section of the tissue-extractionlumen between reduced cross-section region 190B′ and the increasedcross-section region 190A′ of the cutting sleeve 175′ of FIG. 8. Thus,the functionality remains the same whether the cutting electrode element195′ is tubular or partly tubular. In FIG. 8A, the ceramic collar 222′is shown, in one variation, as extending only partially around sleeve175 to cooperate with the radial angle of cutting electrode element195′. Further, the variation of FIG. 8 illustrates that the ceramiccollar 222′ has a larger outside diameter than insulative layer 202.Thus, friction may be reduced since the short axial length of theceramic collar 222′ interfaces and slides against the interfacinginsulative layer 200 about the inner surface of lumen 172 of outersleeve 170.

In general, one aspect of the invention comprises a tissue cutting andextracting device (FIGS. 10A-11C) that includes first and secondconcentric sleeves having an axis and wherein the second (inner) sleeve175 has an axially-extending tissue-extraction lumen therein, andwherein the second sleeve 175 is movable between axially non-extendedand extended positions relative to a tissue-receiving window 176 infirst sleeve 170 to resect tissue, and wherein the tissue extractionlumen 160 has first and second cross-sections. The second sleeve 175 hasa distal end configured as a plasma electrode edge 180 to resect tissuedisposed in tissue-receiving window 176 of the first sleeve 170.Further, the distal end of the second sleeve, and more particularly, theelectrode edge 180 is configured for plasma ablation of a substantiallywide path in the tissue. In general, the tissue-extraction device isconfigured with a tissue extraction lumen 160 having a distal endportion with a reduced cross-section that is smaller than across-section of medial and proximal portions of the lumen 160.

In one aspect of the invention, referring to FIGS. 7A-7B and 9A-9B, thetissue-extraction lumen 160 has a reduced cross-sectional area in lumenregion 190A proximate the plasma cutting tip or electrode edge 180wherein said reduced cross section is less that 95%, 90%, 85% or 80%than the cross sectional area of medial and proximal portions 190B ofthe tissue-extraction lumen, and wherein the axial length of thetissue-extraction lumen is at least 10 cm, 20 cm, 30 cm or 40 cm. In oneembodiment of tissue-cutting device 100 for hysteroscopic fibroidcutting and extraction (FIG. 1), the shaft assembly 140 of thetissue-cutting device is 35 cm in length.

FIGS. 10A-10C illustrate the working end 145 of the tissue-cuttingdevice 100 with the reciprocating cutting sleeve or inner sleeve 175 inthree different axial positions relative to the tissue receiving window176 in outer sleeve 170. In FIG. 10A, the cutting sleeve 175 is shown ina retracted or non-extended position in which the sleeve 175 is at itproximal limit of motion and is prepared to advance distally to anextended position to thereby electrosurgically cut tissue positioned inand/or suctioned into in window 176. FIG. 10B shows the cutting sleeve175 moved and advanced distally to a partially advanced or medialposition relative to tissue cutting window 176. FIG. 10C illustrates thecutting sleeve 175 fully advanced and extended to the distal limit ofits motion wherein the plasma cutting electrode 180 has extended pastthe distal end 226 of tissue-receiving window 176 at which moment theresected tissue strip 225 in excised from tissue volume 220 and capturedin reduced cross-sectional lumen region 190A.

Now referring to FIGS. 10A-10C and FIGS. 11A-11C, another aspect of theinvention comprises “tissue displacement” mechanisms provided bymultiple elements and processes to “displace” and move tissue strips 225in the proximal direction in lumen 160 of cutting sleeve 175 to thusensure that tissue does not clog the lumen of the inner sleeve 175. Ascan be seen in FIG. 10A and the enlarged views of FIGS. 11A-11C, onetissue displacement mechanism comprises a projecting element 230 thatextends proximally from distal tip 232 which is fixedly attached toouter sleeve 170. The projecting element 230 extends proximally alongcentral axis 168 in a distal chamber 240 defined by outer sleeve 170 anddistal tip 232. In one embodiment depicted in FIG. 11A, the shaft-likeprojecting element 230, in a first functional aspect, comprises amechanical pusher that functions to push a captured tissue strip 225proximally from the small cross-section lumen 190B of cutting sleeve 175as the cutting sleeve 175 moves to its fully advanced or extendedposition. In a second functional aspect, the chamber 240 in the distalend of sleeve 170 is configured to capture a volume of saline distendingfluid 244 from the working space, and wherein the existing RF electrodesof the working end 145 are further configured to explosively vaporizethe captured fluid 244 to generate proximally-directed forces on tissuestrips 225 resected and disposed in lumen 160 of the cutting sleeve 175.Both of these two functional elements and processes (tissue displacementmechanisms) can apply a substantial mechanical force on the capturedtissue strips 225 by means of the explosive vaporization of liquid inchamber 240 and can function to move tissue strips 225 in the proximaldirection in the tissue-extraction lumen 160. It has been found thatusing the combination of multiple functional elements and processes canvirtually eliminate the potential for tissue clogging the tissueextraction lumen 160.

More in particular, FIGS. 12A-12C illustrate sequentially the functionalaspects of the tissue displacement mechanisms and the explosivevaporization of fluid captured in chamber 240. In FIG. 12A, thereciprocating cutting sleeve 175 is shown in a medial position advancingdistally wherein plasma at the cutting electrode edge 180 is cutting atissue strip 225 that is disposed within lumen 160 of the cutting sleeve175. In FIG. 12A-12C, it can be seen that the system operates in firstand second electrosurgical modes corresponding to the reciprocation andaxial range of motion of cutting sleeve 175 relative to thetissue-receiving window 176. As used herein, the term “electrosurgicalmode” refers to which electrode of the two opposing polarity electrodesfunctions as an “active electrode” and which electrode functions as a“return electrode”. The terms “active electrode” and “return electrode”are used in accordance with convention in the art—wherein an activeelectrode has a smaller surface area than the return electrode whichthus focuses RF energy density about such an active electrode. In theworking end 145 of FIGS. 10A-11C, the cutting electrode element 195 andits cutting electrode edge 180 must comprise the active electrode tofocus energy about the electrode to generate the plasma for tissuecutting. Such a high-intensity, energetic plasma at the electrode edge180 is needed throughout stroke X indicated in FIG. 12A-12B to cuttissue. The first mode occurs over an axial length of travel of innercutting sleeve 175 as it crosses the tissue-receiving window 176, atwhich time the entire exterior surface of outer sleeve 170 comprises thereturn electrode indicated at 185. The electrical fields EF of the firstRF mode are indicated generally in FIG. 12A.

FIG. 12B illustrates the moment in time at which the distal advancementor extension of inner cutting sleeve 175 entirely crossed thetissue-receiving window 176. At this time, the electrode sleeve 195 andits electrode edge 180 are confined within the mostly insulated-wallchamber 240 defined by the outer sleeve 170 and distal tip 232. At thismoment, the system is configured to switch to the second RF mode inwhich the electric fields EF switch from those described previously inthe first RF mode. As can be seen in FIG. 12B, in this second mode, thelimited interior surface area 250 of distal tip 232 that interfaceschamber 240 functions as an active electrode and the distal end portionof cutting sleeve 175 exposed to chamber 240 acts as a return electrode.In this mode, very high energy densities occur about surface 250 andsuch a contained electric field EF can explosively and instantlyvaporize the fluid 244 captured in chamber 240. The expansion of watervapor can be dramatic and can thus apply tremendous mechanical forcesand fluid pressure on the tissue strip 225 to move the tissue strip inthe proximal direction in the tissue extraction lumen 160. FIG. 12Cillustrates such explosive or expansive vaporization of the distentionfluid 244 captured in chamber 240 and further shows the tissue strip 225being expelled in the proximal direction the lumen 160 of inner cuttingsleeve 175. FIG. 14 further shows the relative surface areas of theactive and return electrodes at the extended range of motion of thecutting sleeve 175, again illustrating that the surface area of thenon-insulated distal end surface 250 is small compared to surface 255 ofelectrode sleeve which comprises the return electrode.

Still referring to FIGS. 12A-12C, it has been found that a single powersetting on the RF source 150 and controller 155 can be configured both(i) to create plasma at the electrode cutting edge 180 of electrodesleeve 195 to cut tissue in the first mode, and (ii) to explosivelyvaporize the captured distention fluid 244 in the second mode. Further,it has been found that the system can function with RF mode-switchingautomatically at suitable reciprocation rates ranging from 0.5 cyclesper second to 8 or 10 cycles per second. In bench testing, it has beenfound that the tissue-cutting device described above can cut and extracttissue at the rate of from 4 grams/min to 8 grams/min without anypotential for tissue strips 225 clogging the tissue-extraction lumen160. In one embodiment, a negative pressure source 125 can be coupled tothe tissue-extraction lumen 160 to apply tissue-extracting forces totissue strips in the lumen.

Of particular interest, the fluid-capture chamber 240 defined by sleeve170 and distal tip 232 can be designed to have a selected volume,exposed electrode surface area, length and geometry to optimize theapplication of expelling forces to resected tissue strips 225. In oneembodiment, the diameter of the chamber is 3.175 mm and the length is5.0 mm which taking into account the projecting element 230, provided acaptured fluid volume of approximately 0.040 mL. In other variations,the captured fluid volume can range from 0.004 to 0.080 mL.

In one example, a chamber 240 with a captured liquid volume of 0.040 mLtogether with 100% conversion efficiency in an instantaneousvaporization would require 103 Joules to heat the liquid from roomtemperature to water vapor. In operation, since a Joule is a W*s, andthe system reciprocate at 3 Hz, the power required would be on the orderof 311 W for full, instantaneous conversion to water vapor. Acorresponding theoretical expansion of 1700× would occur in the phasetransition, which would results in up to 25,000 psi instantaneously(14.7 psi×1700), although due to losses in efficiency andnon-instantaneous expansion, the actual pressures would be less. In anyevent, the pressures are substantial and can apply expelling forcessufficient to the expel the captured tissue strips 225 the length of theextraction channel in the probe.

Referring to FIG. 12A, the interior chamber 240 can have an axial lengthfrom about 0.5 mm to 10 mm to capture a liquid volume ranging from about0.004 mL 0.01 mL. It can be understood in FIG. 12A, that the interiorwall of chamber 240 has an insulator layer 200 which thus limits theelectrode surface area 250 exposed to chamber 240. In one embodiment,the distal tip 232 is stainless steel and is welded to outer sleeve 170.The post element 248 is welded to tip 232 or machined as a featurethereof. The projecting element 230 in this embodiment is anon-conductive ceramic. FIG. 13 shows the cross-section of the ceramicprojecting element 230 which is fluted, which in one embodiment hasthree flute elements 260 in three corresponding axial grooves 262 in itssurface. Any number of flutes, channels or the like is possible, forexample from 2 to about 20. The purpose of this design is to provide asignificant cross-sectional area at the proximal end of the projectingelement 230 to push the tissue strip 225, while at the same time thethree grooves 262 permit the proximally-directed jetting of water vaporto impact the tissue exposed to the grooves 262. In one embodiment, theaxial length D of the projecting element 230 is configured to pushtissue entirely out of the reduced cross-sectional region 190B of theelectrode sleeve element 195. In another embodiment, the volume of thechamber 240 is configured to capture liquid that when explosivelyvaporized provided a gas (water vapor) volume sufficient to expand intoand occupy at least the volume defined by a 10% of the total length ofextraction channel 160 in the device, at least 20% of the extractionchannel 160, at least 40% of the extraction channel 160, at least 60% ofthe extraction channel 160, at least 80% of the extraction channel 160or at least 100% of the extraction channel 160.

As can be understood from FIGS. 12A to 12C, the distending fluid 244 inthe working space replenishes the captured fluid in chamber 240 as thecutting sleeve 175 moves in the proximal direction or towards itsnon-extended position. Thus, when the cutting sleeve 175 again moves inthe distal direction to cut tissue, the interior chamber 240 is filledwith fluid 244 which is then again contained and is then available forexplosive vaporization as described above when the cutting sleeve 175closes the tissue-receiving window 176. In another embodiment, a one-wayvalve can be provided in the distal tip 232 to draw fluid directly intointerior chamber 240 without the need for fluid to migrate throughwindow 176.

FIG. 15 illustrates another variation in which the active electrodesurface area 250′ in the second mode comprises a projecting element 230with conductive regions and non-conductive regions 260 which can havethe effect of distributing the focused RF energy delivery over aplurality of discrete regions each in contact with the captured fluid244. This configuration can more efficiently vaporize the captured fluidvolume in chamber 240. In one embodiment, the conductive regions 250′can comprise metal discs or washers on post 248. In other variation (notshown) the conductive regions 250′ can comprise holes, ports or pores ina ceramic material 260 fixed over an electrically conductive post 248.

In another embodiment, the RF source 150 and controller 155 can beprogrammed to modulate energy delivery parameters during stroke X andstroke Y in FIGS. 12A-12C to provide the optimal energy (i) for plasmacutting with electrode edge 180, and (ii) for explosively vaporizing thecaptured fluid in chamber 240.

FIGS. 16-18 illustrate a fluid management system 500 that can be usedwhen treating tissue in a body cavity, space or potential space 502(FIG. 17). The fluid management system 500 is depicted schematically ina hysteroscopic fibroid treatment system 510 that is adapted for cuttingand extraction of fibroids or other abnormal intra-uterine tissue usinga hysteroscope 512 and tissue-cutting probe 515 that can be similar tothose described above. FIG. 16 depicts the tissue-cutting probe 515 withhandle 516 and extension member 518 with working end 520 (FIG. 17) thatcan be introduced through working channel 522 extending through the body523 and shaft 524 of the hysteroscope 512. FIG. 16 further shows a motor525 in handle 516 of the tissue-cutting probe that is coupled to acontroller and power supply by power cable 526. FIG. 17 illustrates theworking end 520 of the cutting probe 515 in a uterine cavity proximate atargeted fibroid 530.

Referring to FIGS. 16-17, in general, the fluid management system 500comprises a fluid source or reservoir 535 of a distention fluid 244, acontroller and pump system to provide fluid inflows and outflows adaptedto maintain distension of a body space and a filter system 540 forfiltering distention fluid 244 that is removed from the body cavity andthereafter returned to the fluid source 535. The use of a recovered andfiltered fluid 244 and the replenishment of the fluid source 535 isadvantageous because (i) the closed-loop fluid management system caneffectively measure fluid deficit to thereby monitor intravasation andinsure patient safety, (ii) the system can be set up and operated in avery time-efficient manner, and (ii) the system can be compact and lessexpensive to thereby assist in enabling office-based procedures.

The fluid management system 500 (FIG. 16) includes a computer controlsystem that is integrated with the RF control system in an integratedcontroller 545. The controller 545 is adapted to control first andsecond peristaltic pumps 546A and 546B for providing inflows andoutflows of a distention fluid 244, such as saline solution, from source535 for the purpose of distending the body cavity and controlling theintra-cavity pressure during a tissue cutting-extracting procedure asdepicted in FIG. 17. In one embodiment shown in FIGS. 16-18, thecontroller 545 controls peristaltic pump 546A to provide positivepressure at the outflow side 548 of the pump (FIG. 17) to provideinflows of distention fluid 244 through first flow line 550 which is incommunication with fitting 561 and fluid flow channel 108 a inhysteroscope 515. The flow channel 108 a is described above in aprevious embodiment and is illustrated in FIG. 3 above. The controller545 further controls the second peristaltic pump 546B to providenegative pressure at the inflow side 552 of the pump (FIG. 17) to thesecond line 555 to assist in providing outflows of distention fluid 244from the body cavity 502. As described above, the explosive vaporizationof fluid in the working end 525 of cutting probe 515 functions to expeltissue strips 225 proximally in the extraction channel 160 of cuttingsleeve 175, which can operate in conjunction with negative pressures inline 555 provided by pump 546B. In operation, the second peristalticpump 546B also operates to provide positive pressure on the outflow side556 of pump 546B in the second flow line portion 555′ to pump outflowsof distention fluid 244 through the filter system 540 and back to thefluid source 535.

In one system embodiment, the controller 545 operates to controlpressure in cavity 502 by pressure signals from a pressure sensor 560that is coupled to a fitting 562 in hysterocope 512 which communicateswith a flow channel 108 b (see FIG. 16) that extends through thehysteroscope. In one embodiment, the flow channel 108 b has a diameterof at least 1.0 mm to allow highly accurate sensing of actualintra-cavity pressure. In prior art commercially-available fluidmanagement systems, the intra-cavity pressure is typically estimated byvarious calculations using known flow rates through a pump or remotepressure sensors in the fluid inflow line that can measure backpressures. Such prior art fluid management systems are stand-alonesystems and are adapted for use with a wide variety of hysteroscopes andendoscopes, most of which do not have a dedicated flow channel forcommunicating with a pressure sensor. For this reason, prior art fluidmanagement systems rely on algorithms and calculations to only estimateintra-cavity pressure.

In one embodiment, as depicted in FIG. 16, the pressure sensor 560 isdisposable and is operatively coupled to controller 545 by cable 564. Inone embodiment, the sensor can be a piezoresistive silicon pressuresensor, Model No. 1620, available from Measurement Specialties. Ltd.,45738 Northport Loop West, Fremont, Calif. 94538.

FIG. 17 schematically illustrates the fluid management system 500 inoperation. The uterine cavity 502 is a potential space and needs to bedistended to allow for hysteroscopic viewing. A selected pressure can beset in the controller 545, for example via a touch screen 565, which thephysician knows from experience is suited for distending the cavity 502and/or for performing a procedure. In one embodiment, the selectedpressure can be any pressure between 0 and 150 mm Hg. In one systemembodiment, the first pump 546A can operate as a variable speed pumpthat is actuated to provide a flow rate of up to 850 ml/min throughfirst line 550. In this embodiment, the second pump 546B can operate ata fixed speed to move fluid in the second line 555. In use, thecontroller 545 can operate the pumps 546A and 546B at selected matchingor non-matching speeds to increase, decrease or maintain the volume ofdistention fluid 244 in the uterine cavity 502. Thus, by independentcontrol of the pumping rates of the first and second peristaltic pumps546A and 546B, a selected set pressure in the body cavity can beachieved and maintained in response to signals of actual intra-cavitypressure provided by sensor 560.

In one system embodiment, as shown in FIGS. 17-18, the fluid managementsystem 500 includes a filter module or system 540 that can include afirst filter or tissue-capturing filter 570 that is adapted to catchtissue strips 225 that have been cut and extracted from the body cavity502. A second filter or molecular filter 575, typically a hollow fiberfilter, is provided beyond the first filter 570, wherein the molecularfilter 575 is adapted to remove blood and other body materials from thedistention fluid 244. In particular, the molecular filter 575 is capableof removing red blood cells, hemoglobin, particulate matter, proteins,bacteria, viruses and the like from the distention fluid 244 so thatendoscopic viewing of the body cavity is not obscured or clouded by anysuch blood components or other contaminants. As can be understood fromFIGS. 16-18, the second peristaltic pump 546B at its outflow side 556provides a positive pressure relative to fluid flows into the filtermodule 540 to move the distention fluid 244 and body media through thefirst and second filters, 570 and 575, and in a circulatory flow back tothe fluid source 535.

Referring to FIG. 18, in an embodiment, the first filter 570 comprises acontainer portion or vial 576 with a removable cap 577. The inflow ofdistention fluid 244 and body media flows through line portion 555 andthrough fitting 578 into a mesh sac or perforate structure 580 disposedin the interior chamber 582 of the vial 576. The pore size of theperforate structure 580 can range from about 200 microns to 10 microns.The lumen diameter of hollow fibers 585 in the second filter 575 can befrom about 400 microns to 20 microns. In general, the pore size ofperforate structure 580 in the first filter 570 is less than thediameter of the lumens of hollow fibers 585 in the second filter 575. Inone embodiment, the pore size of the perforate structure 580 is 100microns, and the lumen size of the hollow fibers 585 in the molecularfilter 575 is 200 microns. In one embodiment, the molecular filter 575is a Nephros DSU filter available from Nephros, Inc., 41 Grand Ave.,River Edge, N.J. 07661. In one variation, the filter 575 is configuredwith hollow fibers having a nominal molecular weight limit (NMWL) ofless than 50 kDa, 30 kDa or 20 kDa.

In another aspect of the invention, the molecular filter 575 isconfigured to filter large volumes of distention fluid, since the fluidflows are circulating. Additionally, the molecular filter 575 isconfigured to filter significant potential volumes of distention fluidthat may contaminated with blood, blood products and the like that willbe mixed with the fluid. In one embodiment, the molecular filter 575 hasa membrane surface area of at least 0.6 m², 0.8 m², 1.0 m², 1.2 m² and1.4 m², wherein the membrane surface area is defined as the totalsurface area of the lumens of the hollow fibers 585 in the molecularfilter 575. In another aspect of the invention, a method of fluidmanagement can include distending a body space and maintaining a flowrate of up to 850 ml/min of a distension fluid flow into and out of abody space and thereafter through a filter system 540 capable ofremoving at least 20 ml, 40 ml or 60 ml of blood from the distensionfluid 244.

Referring to FIG. 18, it can be seen that the filter module 540 includesdetachable connections between the various fluid flow lines to allow forrapid coupling and de-coupling of the filters and flow lines. More inparticular, flow line 555 extending from the tissue-cutting probe 515has a connector portion 592 that connects to inlet fitting 578 in thefirst filter 546A. Flow line portion 555′ that is intermediate thefilters 546A and 546B has connector portion 596 a that connects tooutlet fitting 596 b in first filter 542A. The outflow end of flow line555′ has connector 598 a that connects to inlet fitting 598 b of thesecond filter 546B. The return flow line 600 that is intermediate thesecond 546B and fluid source 535 has connector portion 602 a thatconnects to outlet fitting 602 b in second first filter 546B. In oneembodiment, at least one check valve 605 is provided in the flow pathintermediate the filters 546A, 546B which for example can be in line555′, connectors 596 a, 598 a or fittings 596 b, 598 b. In FIG. 18, acheck valve 605 is integrated with the inlet end 608 of the secondfilter 546B. In use, the operation of the system will result insubstantial fluid pressures in the interior of the second filter, andthe check valve 605 allows for de-coupling the first filter withoutescape of pressure and release of fluid media into the environment, forexample, when the tissue cutting procedure is completed and thephysician or nurse wishes to transport the vial 576 and tissue strips225 therein to a different site for biopsy purposes.

In one aspect, a fluid management system comprising a first fluid line550 configured to carry distention fluid 224 or influent from a fluidsource 535 to a body space, a second fluid line 555, 555′ and 560configured to carry fluid from the body space to a first filter 570 andthen to a second filter 575 and then back to the fluid source 535, apump operatively coupled to the second fluid line to move the fluid andat least one check valve 605 in the second fluid line intermediate thefirst and second filters 570 and 575.

In one embodiment, the controller 545 of the fluid management system 500is configured for calculation of a fluid deficit that is measured as adifference between a fluid volume delivered to the body space 502 and afluid volume recovered from the body space during a medical proceduresuch as fibroid removal (see FIGS. 16-17). A method of fluid managementin a hysteroscopic procedure comprises providing a distention fluidsource 535 (FIG. 17) having a predetermined volume, introducing fluid(e.g., saline) from the source 535 through a first flow path or line 550into the uterine cavity and through a second flow line 555 out of thecavity into a filter module 540 and through a further portion 600 of thesecond flow line back to the fluid source 535 wherein the interiorvolume of the first and second flow lines and the filter module whensubtracted from the predetermined volume of the source 535 equals 2.5liters or less to thereby insure that saline intravasion is less than2.5 liters. In this variation, the predetermined volume of the source535 can be 3.0 liters, as in a standard 3 liter saline bag, and theinterior system volume can be at least 0.5 liters.

While certain embodiments of the present invention have been describedabove in detail, it will be understood that this description is merelyfor purposes of illustration and the above description of the inventionis not exhaustive. Specific features of the invention are shown in somedrawings and not in others, and this is for convenience only and anyfeature may be combined with another in accordance with the invention. Anumber of variations and alternatives will be apparent to one havingordinary skills in the art. Such alternatives and variations areintended to be included within the scope of the claims. Particularfeatures that are presented in dependent claims can be combined and fallwithin the scope of the invention. The invention also encompassesembodiments as if dependent claims were alternatively written in amultiple dependent claim format with reference to other independentclaims.

What is claimed is:
 1. A medical fluid management system, comprising: afluid source having an initial volume; a filter system having a fluidretention volume; a first fluid line configured to carry distentionfluid from the fluid source to a body space, said first fluid linehaving a fluid retention volume; second and third fluid lines configuredto re-circulate fluid from the body space through the filter system andback to the fluid source, said second and third fluid lines having afluid retention volume; an inflow pump configured to deliver distentionfluid from the fluid source through the first fluid line to the bodyspace; an outflow pump configured to deliver distention fluid from thebody space through the filter system and second and third fluid linesback to the fluid source; a controller configured to control the inflowand outflow pumps; wherein the controller is configured to shut down theinflow and outflow pumps when a difference between (1) the initialvolume of the fluid source and (2) a sum of a volume of fluid in thefluid source present at a given time and the combined fluid retentionvolumes of the filter system and first, second and third fluid linesexceeds a preselected volume.
 2. The system of claim 1, wherein thepreselected volume is 2.5 liters.
 3. The system of claim 2, wherein thecombined fluid retention volumes of the filter system and first, secondand third fluid lines is at least 0.5 liters.
 4. The system of claim 2,wherein the initial volume of the fluid source is 3 liters.
 5. Thesystem of claim 1, wherein the combined fluid retention volumes of thefilter system and first, second and third fluid lines is at least 0.5liters.
 6. The system of claim 1, wherein the filter system includes atissue capturing filter and a molecular filter.
 7. The system of claim6, further comprising a check valve fluidly coupled between the tissuecapturing filter and the molecular filter.
 8. The system of claim 6,wherein the check valve is located at an inlet of the molecular filter.9. A medical fluid management system, comprising: a fluid source havingan initial volume; a filter system having a fluid retention volume; afirst fluid line configured to carry distention fluid from the fluidsource to a body space, said first fluid line having a fluid retentionvolume; second and third fluid lines configured to re-circulate fluidfrom the body space through the filter system and back to the fluidsource, said second and third fluid lines having a fluid retentionvolume; an inflow pump configured to deliver distention fluid from thefluid source through the first fluid line to the body space; an outflowpump configured to deliver distention fluid from the body space throughthe filter system and second and third fluid lines back to the fluidsource; a controller configured to control the inflow and outflow pumps;wherein the controller is configured to monitor a difference between:(1) the initial volume of the fluid source; and (2) a sum of a volume offluid in the fluid source present at a given time and the combined fluidretention volumes of the filter system and first, second and third fluidlines; wherein the controller is configured to sound an alarm when thedifference exceeds a preselected volume.
 10. The system of claim 9,wherein the preselected volume is 2.5 liters.
 11. The system of claim10, wherein the combined fluid retention volumes of the filter systemand first, second and third fluid lines is at least 0.5 liters.
 12. Thesystem of claim 10, wherein the initial volume of the fluid source is 3liters.
 13. The system of claim 9, wherein the combined fluid retentionvolumes of the filter system and first, second and third fluid lines isat least 0.5 liters.
 14. The system of claim 9, wherein the filtersystem includes a tissue capturing filter and a molecular filter. 15.The system of claim 14, further comprising a check valve fluidly coupledbetween the tissue capturing filter and the molecular filter.
 16. Thesystem of claim 14, wherein the check valve is located at an inlet ofthe molecular filter.
 17. A medical fluid management system, comprising:a fluid source having an initial volume; a filter system having a fluidretention volume; a first fluid line configured to carry distentionfluid from the fluid source to a body space, said first fluid linehaving a fluid retention volume; second and third fluid lines configuredto re-circulate fluid from the body space through the filter and back tothe fluid source, said second and third fluid lines having a fluidretention volume; and a controller which monitors a difference between(1) the initial volume of the fluid source and (2) a sum of a volume offluid in the fluid source present at a given time and the combined fluidretention volumes of the filter system and first, second and third fluidlines, wherein a difference that exceeds a preselected volume indicatesa risk of intravasion.
 18. The system of claim 17, wherein thepreselected volume is 2.5 liters.
 19. The system of claim 18, whereinthe combined fluid retention volumes of the filter system and first,second and third fluid lines is at least 0.5 liters.
 20. The system ofclaim 18, wherein the initial volume of the fluid source is 3.0 liters.